Researchers have shown that optical coherence tomography angiography (OCT-A) images reveal microvasculature changes to the superficial capillary plexus (SCP) and deep capillary plexus (DCP) of patients with higher levels of risk for obstructive sleep apnea syndrome (OSAS). The parafoveal and peripapillary vessel densities and flow area indices were reduced in the DCP and increased in the SCP of patients at high risk for OSAS, according to a newly published study in the American Journal of Ophthalmology. The authors note that, while these findings suggest an association between vasculature changes in the eye and disease severity, OCT-A should not be used to determine the severity of the OSAS.

Several studies have shown a link between OSAS and ocular pathologies, such as non-arteritic anterior ischemic optic neuropathy, retinal vein occlusions, central serous chorioretinopathy, severe retinopathy in patients with diabetes, and more severe forms of macular edema and glaucoma, according to the authors. Here, researchers sought to further explore the link between the syndrome and retinal microvasculature. 

The investigators conducted a prospective, cross-sectional study using OCT-A imaging to examine the retinal vessel changes at peripapillary and parafoveal regions in patients with varying degrees of OSAS. The study’s 303 participants were divided into 3 groups (mild, intermediate, and severe risk) based on their sleep apnea risk score, which was determined using the STOP-BANG questionnaire

In the group with the highest OSAS risk, an increase in flow areas (P=0.011) and vessel densities (P=0.002) in SCP were found. Flow areas (P= 0.003) and vessel densities (P<0.000) in DCP were reduced. These variations in vessel densities in both the layers were noted in all of the 8 parafoveal regions of the high risk subjects. A negative correlation between sleep scores and flow areas (P=0.003) and vessel densities (P=<0.001) in DCP also were recorded.


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The STOP-BANG questionnaire quantifies the severity of OSAS based on 4 yes-or-no questions, and 4 additional metrics. Patients with high refractive errors, astigmatism, , glaucoma, ocular trauma, any history of intraocular surgery, or congenital optic nerve head affection were excluded. Those with macular edema or any other macular pathology or those with optic nerve head pathologies or retinal nerve fiber layer loss secondary to glaucoma also were excluded from the study.

The authors note that a limitation of the study could be the lack of polysomnography-derived sleep study data for these patients and its correlation to vessel densities and flow on OCT-A. However, they contend that the high sensitivity of the sleep apnea questionnaire in predicting risk is adequate for analyzing retinal vessel changes. They also note that OCT-A itself has a few limitations, including a very small degree of visual field around the fovea, that the test cannot be performed on sleeping patients, and that OCT-A images of retinal vessels are obtained from reconstructions of many scans by the split-spectrum amplitude-decorrelation angiography algorithm, providing quantitative data of the vascular flow and vessel density.

Reference

Venkatesh R, Pereira A, Aseem A, et al. Association between sleep apnoea risk score and retinal microvasculature using optical coherence tomography angiographyAm J Ophthalmol. [Published online August 31, 2020]. doi: 10.1016/j.ajo.2020.08.037